A Graph Model for Pattern-Sensitive Faults in Random Access Memories

This correspondence generalizes Hayes' recent ideas for generating an optimal transition write sequence which forms the "backbone" of his algorithm for testing semiconductor RAM's for pattern-sensitive faults. The generalization, presented in graph theoretic terms, involves two sequential steps. The frmst step results in assigning of a "color" to each memory cell. In the second step, each color is defined as a distinct sequence of bits representing the sequence of states assumed by the correspondingly colored cell. The constraints imposed at each step lead to interesting and general problems in graph theory: the standard graph coloring problem in the first step, and a path projection problem from a binary m-cube to a subcube in the second step. Applications to arbitrary k-cell neighborhoods, and particularly to three-cell neighborhoods are shown.